Skins and method of dehairing



Patented Apr. 18, 1944 SKINS AND METHOD OF DEHAIRING Edward F. Christopher, Chicago, 11]., assignor to Industrial Patents Corporation, Chicago, Ill., a corporation of Delaware No Drawing. Application May 22, 1942,

Serial No. 444,103

22 Claims.

This invention relates to a method of treatin hides and skins to prepare the hides and skins for the subsequent taming process.

The older conventional method of treating hides and skins for the removal of hair or wool consists of soaking the hides or skins in a lime bath for from about five days to seven days. At

the end of this soaking period the hides are removed and thoroughly washed. The hides are then subjected to a beaming operation in which the hides are scraped or beamed with a dull knife or blade to remove the hair and to squeeze out any Wool or hair roots, This operation simultaneously removes foreign materials and dirt from the skin but it is a costly operation because it is of necessity -a hand operation. -In this method for removing hair and wool a considerable time is required and large spaces must be provided for th tanks in which the hides are treated with the lime liquor.

Numerous methods have been employed and have been proposed to hasten the dewooling and dehairing process or to provide a method of removing the hair or wool in a shorter period of time. Perhaps the most commonly used method of treating hides and skins for the removal of hair or wool consists of what may b classed as a two stage method including dewooling and dehairing the pelts. The skins or hides are dewooled by painting or treating the flesh side of the hide or skin with a depilatory consisting of a paste containing lime, sodium sulfide and water.

The paste is generally prepared by mixing slaked lime with powdered sodium sulfide in a ratio of about 60 parts of lime to 40 parts of sulfide and adding suificient water so that the paste may be painted on the skin or hide with a brush. The

. treated skins are then allowed to remain in a main. The skins treated with the depilatory and from which the wool has been pulled are generallyknown as dewooled skins.

The dewooled skins are then "dehaired by by the hides are agitated in the bath for a willcient period of time to substantially remove the remaining fine hair and wool and the remaining hair or wool roots. This method of treating hides and skins permits the removal of the hair and wool in from two days to three days, however, the

skins are afiected to a much greater extent than in the older conventional method.

One of the principal objections to this method is that'the skins 'become drawn. This condition produces a loose grained leather and one side of the hide appears to draw or shrink to a greater extent than the other surface. The other principal objection to skins processed in this manner is that they do not possess the same degree of stretch or elasticity as skins Processed in accordance with the older conventional manner.

Numerous compositions have been proposed, including the use of various enzymes, various organic materials and various inorganic salts, for

the treatment of dewooled hides and skins to aid in removing the remaining fin hair and remaining hair roots. However, these substances are in many instances too costly for commercial application, and many of the substances are so severe in their action that they injure th skin although a close control of the process is attempted.

The principal object of the present invention is to provide a method whereby the removal of hair and wool may be accomplished in a shorter vperiod of time than the older lime method but which produces a type of skin which is substan tially the same as thetype of skin produced by this old method.

Another of the objects of this invention is to provide a method for treating dewooled hides and skins which is more eflicient in the removal Another object of this invention is to provide a method of treating dewooled hides and skins for the removal of residual hair and hair or wool roots so as to yield a higher quality hide or skin for the subsequent preparation of leather.

The present invention contemplates the addition to an alkaline-sodium sulfide dehairing liquor of a small proportion of cyanamide and water soluble compounds and derivatives of cyanamide;

Calcium and sodium cyanamides may be set forth as illustrative examples of satisfactory compounds. Derivatives which are satisfactory include dicyandiamide, methyl and ethyl derivatives such as dimethyl and diethyl cyanamides,

and phenyl derivatives such as diphenyl carboditinued for about one-half hour.

imide and cyananilide. These examples are merely illustrative and it is obvious that other substances are satisfactory. The term water soluble is used to designate a sufiicient solubility to form an aqueous solution of the required concentratlon for the purposes of this invention.

It is well-known that the ordinary conventional alkaline solutions or suspensions of sodium sulfide are relatively slow in their dehairing action and various reagents have been added in an attempt to increase the rate of dehairing. However, these substances are generally injurious to the hides and skins. The reagents employed in the practice of the present invention are not injurious to the hides and skins, and, in general, permit the use of smaller quantities of lime and sodium sulfide. In the practice of the-present invention the reagent is added to the dehairing liquor, preferably during treatment of the hides with the liquor.

The liquor is first prepared by dissolving from about 0.1 per cent to 1.3 per cent, preferably from about 0.3 per cent to 0.5 per cent, sodium sulfide in water. The dewooled hides or skins are then soaked in this solution, about 3 parts to 4 parts by weight of solution being employed for .about each part by weight of hides or skins. The

hides are reeled in this liquor or solution for about one hour. Lime is then added in the proportion of from about 1 per cent to 5 per cent, based upon the weight of the solution, and the hides are again reeled for about one-half hour. The reagent is then added to and dissolved in the solution and the skins or hides again reeled for about one hour. remain in the liquor for from 16 hours to 24 hours after which they are again reeled to remove the swollen o: pulped wool and hair. The hides are then separated from the liquor, thor oughly rinsed and are ready for the subsequent bating and pickling operations."

It is obvious to those skilled in the art that the proportions which are set forth are not critical and may be varied. The reagents employed in the practice of the present invention are preferably employed in quantities between 0.1 per cent and 0.5 per cent. For certain special purposes it may be desirable to employ as much as per cent of a particular reagent or less than 0.l-per cent of a particular reagent.- The smaller proportions are, of course, desirable from an pounds of the dewooled skins were soaked in about 280 pounds of sodium sulfide solution containing between 0.3 per centand 0.35 per cent sodium sulfide. The skins were reeled in this solution for about one hour and aboutl per cent lime based upon the weight of the; solution was added directly to the liquor. Reeling was con- About 0.1 per cent cyanamide, calcium cyanamide or dicyandiamide was then added and reeling continued for a further period of about one hour. The skins were then allowedto soak in this liquor over night. The following morning. it was found that the greater proportion of hair and wool remaining after dewooling had been removed or The hides are then allowed to from the skins and the skins thoroughly washed with water.

Skins treated in accordance with the described method of dehairing are free from all hair and hair roots and appear to remain unaffected in all other respects. The skins are not drawn and they possess about the same stretch or elasticity as skins processed by the straight lime method.

The precise nature of the action of the pai'-' ticular reagents is not understood. However, the reagents greatly accelerate the dissolving or pulping of the hair and hair roots remaining after dewooling. At the same time the action is not so severe that it injures in any way the skins or hides. The improvements in the dehaired skins may be due to the lower alkalinity of the dehairing bath or solution as compared to the conventional dehairing solutions.

The term dewooled skins" is employed herein and in the claims to, designate hides and skins which have been subjected to the first stage in the method. of removing hair and wool. This stage comprises treating the hide or skin with a depilatory and subjecting the treated hideor skin to mechanical action whereby the major portion of the hair and'wool is removed. The term dewooling is used to designate this first stage in the removal of hair and wool from hides and skins.

The term dehaired skins is used herein and in the claims to designate dewooled skins which have been subjected to a treatment which removes the hair and wool remaining after the dewooling stage. The term dehairing is used to designate the second stage in the removal of hair and wool from hides and skins.

It is to be understood that the foregoing specific examples are not intended'as limitations, but have been set forth as being merely illustrative of the invention. Various modifications ,will suggest themselves to those skilled'in the art and may be made without departing from the spirit and scope of this invention. For example, it is obvious to those skilled in the art that sulfides other than sodium sulfide, such as potassium or ammonium sulfides, might be used in ,the dehairing bath.

I claim:

1. In a method of removing hair and wool from hides and skins, the step which comprises subjecting the hides and skins to the action of anaqueous alkaline medium containing lime, an al-' kali sulfide and a substance selected from the group consisting of cyanamide and-water soluble compounds and derivatives of cyanamide.

v 2. In a'method of removinghair and wool from hides and skins, the step which comprises subjecting the hides and skins to the actionof "an aqueous alkaline solution containing lime, analkali sulfide and a smallproportion of a substance selected from the group consisting ofeyanamlde and water soluble compounds and derivatives or cyanamide.

3. In a, method of removing hair'and wool from hides and skins, thestep which comprises 's'ub jecting dewooled hides and skins to the action of an aqueous medium containing lime,sodium sulfide and a substance selected from the group dissolved. However, to remove the remaining pulped wool and hair, the skins were reeled for about one hour after which the liquor was drained consisting of cyanamide and water soluble com-' pounds and derivatives of cyanamide.

4. In a method of removing hair and wool'from hides and skins, the step which comprises subjecting dewooled hides and skins to the action of an aqueous medium containing lime, sodium sulfide and up to 10 per ce'nt of a substance selected from the group consisting of cyanamide and water soluble compounds and derivatives of cyanamide.

5. In a method of removing hair and wool from hides and skins, the step which comprises soaking dewooled hides and skins in an aqueous solution containing about 1 per cent to about 5 per cent lime, about 0.1 per cent to about 1.3 per cent sodium sulfide and about 0.1 per cent to about 0.5 per cent of a substance selected from the group consisting of cyanamide and water soluble compounds and derivatives of cyanamide.

6. In a, method of removing hair and wool from hides and skins, the step which comprises subjecting dewooled hides and skins to the action of an aqueous alkaline medium containing lime, an alkali sulfide and calcium cyanamide.

7. In a method of removing hair and wool from ludes and skins, the step which comprises soaking dewooled hides and skins in an aqueous solution containing about 1 per cent to about 5 per cent lime, about 0.3 per cent to about 0.5 per cent sodium sulfide and about 0.1 per cent to about 0.5 per cent calcium cyanamide.

8. In a method of removing hair and wool from hides and skins, the step which comprises subjecting dewooled hides and skins to the action of an aqueous alkaline medium containing lime, an alkali sulfide and sodium cyanamide.

9. In a method of removing hair and wool from hides and skins, the step which comprises soaking dewooled'hides and skins in an aqueous solution containing about 1 per cent to about 5 per cent lime, about 0.3 per cent to about 0.5 per cent sodium sulfide and about 0.1 per cent to about 0.5, per cent sodium cyanamide.

10. In a method of removing hair and wool from hides and skins, the step which comprises subjecting dewooled hides and skins to the action of an aqueous alkaline medium containing lime, an alkali sulfide and dicyandiamide.

11. In a method of removing hair and wool from hides and skins, the step which comprises soaking dewooled hides and skins in an aqueous solution containing about 1 per cent to about 5 per cent lime, about 0.3 per cent to about 0.5 per cent sodium sulfide and about 0.1 per cent to about 0.5 per cent dicyandiamide.

12. In a method of removing hair and wool from hides and skins! the steps of soaking dewooled hides and skins in an aqueous solution of sodium sulfide. adding lime to the aqueous solution and reeling the hides and skins in the resulting liquor, adding a small proportion of a substance selected from the class consisting of cyanamide and water soluble compounds and derivatives of cyanamide, soaking the hides and skins in the resulting liquor for a suflicient period of time to dissolve a substantial portion of the hair, reeling the hides and skins in the liquor and thereafter washing the hides and skins.

13. The method of accelerating the dehairing of dewooled hides and skins by the use of limesulfide dehairing liquors, which comprises adding to thedehairing liquor an amount of a substance selected from the group consisting of cyanamide and water soluble compounds and derivatives of cyanamide.

14. The method of accelerating the dehairing of dewooled hides and skins by the use of limesulfide dehairing liquors, which comprises adding to the dehairing liquor a small proportion of calcium cyanamide.

15. The method of accelerating the dehairing of dewooled hides and skins by the use of limesulfide dehairing liquors, which comprises adding to the dehairing liquor a small proportion of sodium cyanamide.

16. The method of accelerating the dehairing of dewooled hides and skins by the use of limesulfide dehairing liquors, which comprises adding to the dehairing liquor a small proportion of v dicyandiamide.

1'7. In a method of dehairing dewooled hides and skins by the action of an alkaline medium containing lime and sodium sulfide, the improvement which comprises adding to the alkaline medium an amount of a substance selected from the group consisting of cyanamide and water soluble compounds and derivatives of cyanamide.

18. A dehairing liquor comprising lime, an alkali sulfide and a substance selected from the group consisting of cyanamide andwater soluble compounds and derivatives of cyanamide.

19. A dehairing liquor comprising lime, sodium sulfide and a substance selected from the group consisting of cyanamide and water soluble compounds and derivatives of cyanamide.

20. A dehairing liquor comprising lime, sodium sulfide and calcium cyanamide.

21. A dehairing liquor comprising lime,

sodium sulfide and sodium cyanamide.

22. A dehairing liquor comprising lime, sodium 

